1. Field of the Invention:
The present invention relates to a gun-launched ramjet projectile, and more particularly, to a ramjet projectile with improved stability, increased probability of hitting a target and increased terminal effectiveness at the target.
2. Description of the Prior Art:
Ramjet propulsion devices are known generally. Characteristics of ramjets have been utilized in numerous prior art devices. In general, a ramjet is a type of engine which utilizes the velocity of the device through the atmosphere to compress air within a combustion chamber. The air then mixes with a fuel, either solid or liquid, within a combustion chamber. As the incoming air is compressed, its temperature is raised sufficiently high to initially combust the fuel which continues to burn due to the movement of air through the device. A suitably sized and shaped nozzle is provided at the rear of the combustion chamber and the heated air and products of the combustion pass through the nozzle forming a stream of high velocity gases. The thrust imparted to the projectile is thus the result of the high velocity gases which are exhausted from the nozzle at the rear of the projectile.
One application of a ramjet powered projectile would be for tank-fired, high-explosive, anti-armor munitions. Conventional, unguided, high-explosive, anti-tank (HEAT) projectiles are unpowered after leaving the cannon barrel. One reason is that if a rear-mounted propulsion system (such as a pusher rocket) is used on such a projectile, the thrust is applied relatively far from the projectile's center of gravity and so large turning moments can be generated by small fluctuations in the thrust. These turning moments tend to deflect the projectile off course. The effect of thrust and other asymmetries can be reduced by rolling the projectile so that the deflections are averaged out. However, high spin rates are detrimental to the operation of shaped-charged warheads contained in the projectile and to the combustion process performance of the ramjet engine. For these reasons, unguided HEAT shells fired from tanks are generally unpowered and launched at high velocity but decelerate fairly rapidly in flight. The result is a long time-of-flight to distant targets. In the time elapsed between launch and impact, the target may move or the shell may drift off-target in a cross wind.
A conventional HEAT projectile has a structure designed primarily to withstand the stresses it experiences at launch and is fuzed to explode nearly instantaneously on contacting the target. The bodies of such shells have little potential for armor-piercing because of their light construction. Such shells generally rely on shaped-charge jets to penetrate armor; as a consequence, light weight armors composed of spaced thin plates can defeat conventional HEAT projectiles which explode on the outer surface of the armor outer armor plate and the vehicle's skin.
The present invention locates the exhaust nozzle of the ramjet engine near the center of gravity of the projectile thus variations in thrust have a very small moment arm to deflect the projectile off course. This also allows the spin rate of the projectile to be greatly reduced with no decrease in projectile stability.